Alfred Hitchcock's reputation as a filmmaker was already on the rise when he died 32 years ago. Since then it has consistently (and rightly) grown ever greater. At the same time, his reputation as a person has taken a lot of blows ... whether rightly or not is a determination way above my pay grade. It's significant that Donald Spoto's biography — the first Hitchcock bio to be published after his death — was subtitled “The Dark Side of Genius.”

Sacha Gervasi's new “Hitchcock” is technically based on Stephen Rebello's “Alfred Hitchcock and the Making of Psycho,” but it draws on decades of lore about the great director's obsessions — the most disturbing being his attempts to win the love of the young blond actresses he repeatedly cast.

Gervasi's movie opens with Hitchcock (Anthony Hopkins, in a fat suit and a bald wig) basking in the critical and commercial success of “North by Northwest,” his 46th feature in 35 years. In the public's mind, it's the ultimate “Hitchcock movie” — although such a concept is an insult to the breadth of his work. It also guarantees that any future films will be seen as disappointing. He decides to make a 180-degree pivot from the glossy, witty style of “North by Northwest” by making a relatively low-budget horror film from Robert Bloch's novel “Psycho.” The rest, as they say, is film history.

While this is going on, age and romantic frustration seem to drive Hitchcock's imagination into the realm of lunacy. Ed Gein (Michael Wincott), the murderer who inspired “Psycho,” is securely confined in a mental hospital, yet he apparently has time to materialize at odd moments and chew the fat (as it were) with Hitch, mostly about girl problems.

The movie is rarely wrong on facts, but manages to be wrong (or, at least, egregiously speculative) on everything else. Let's start with the casting: Daniel Day-Lewis might have had a tall order embodying Lincoln, but he didn't have to worry about the voice. Hopkins, on the other hand, has to look and sound like Hitchcock, who — thanks to his TV series — imprinted his distinct voice on the public, as well as his image. Hopkins gives us a not-very-convincing impression; on the up side, his Hitchcock never lapses into a slight Welsh accent like his Nixon.

Hopkins is — or at least appears — substantially taller than Hitchcock. This is not just a nitpick: Hitchcock's psychology reflects, among other things, a short man's insecurity. Toby Jones — who portrayed him in “The Girl,” a recent HBO movie covering related material — is closer to the mark. Neither matches Hitchcock physically as much as Mike Leigh regular Timothy Spall, a terrific actor, who was initially supposed to play the role in “The Girl.”

A similar, even more emphatic, miscasting is Helen Mirren as Alma Reville, the director's wife. Mirren is way too tall and way, way too glamorous for the real Alma. (Imelda Staunton, who is far closer in size and look, played Alma in the HBO film.) James D'Arcy, however, is perfect as Tony Perkins, and Scarlett Johansson captures Janet Leigh, despite looking little like her.

Having now detailed what's wrong with “Hitchcock,” let me confess that it's pretty entertaining. It's best to approach the film, not as a biopic with elements of a fantasy, but as a fantasy with elements of a biopic. Between the spectral Ed Gein scenes and Hitchcock's habit of speaking to us in the audience, it's frankly a little on the silly side, like a more timid version of Ken Russell's approach in “Mahler” or “The Music Lovers.” If you're a film scholar, it's likely to drive you nuts. But if you enter unburdened by too much knowledge about the title character, there's much to enjoy.

ANDY KLEINis the film critic for Marquee. He can also be heard on “FilmWeek” on KPCC-FM (89.3).